fix!: update eval-tasks -> benchmarks (#1032)

# What does this PR do?

- Update `/eval-tasks` to `/benchmarks`
- ⚠️ Remove differentiation between `app` v.s. `benchmark` eval task
config. Now we only have `BenchmarkConfig`. The overloaded `benchmark`
is confusing and do not add any value. Backward compatibility is being
kept as the "type" is not being used anywhere.

[//]: # (If resolving an issue, uncomment and update the line below)
[//]: # (Closes #[issue-number])

## Test Plan
- This change is backward compatible 
- Run notebook test with

```
pytest -v -s --nbval-lax ./docs/getting_started.ipynb
pytest -v -s --nbval-lax ./docs/notebooks/Llama_Stack_Benchmark_Evals.ipynb
```

<img width="846" alt="image"
src="https://github.com/user-attachments/assets/d2fc06a7-593a-444f-bc1f-10ab9b0c843d"
/>



[//]: # (## Documentation)
[//]: # (- [ ] Added a Changelog entry if the change is significant)

---------

Signed-off-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>
Signed-off-by: Ben Browning <bbrownin@redhat.com>
Signed-off-by: Sébastien Han <seb@redhat.com>
Signed-off-by: reidliu <reid201711@gmail.com>
Co-authored-by: Ihar Hrachyshka <ihar.hrachyshka@gmail.com>
Co-authored-by: Ben Browning <ben324@gmail.com>
Co-authored-by: Sébastien Han <seb@redhat.com>
Co-authored-by: Reid <61492567+reidliu41@users.noreply.github.com>
Co-authored-by: reidliu <reid201711@gmail.com>
Co-authored-by: Yuan Tang <terrytangyuan@gmail.com>

docs/source/concepts/evaluation_concepts.md

@@ -5,7 +5,7 @@ The Llama Stack Evaluation flow allows you to run evaluations on your GenAI appl
 We introduce a set of APIs in Llama Stack for supporting running evaluations of LLM applications.
 - `/datasetio` + `/datasets` API
 - `/scoring` + `/scoring_functions` API
-- `/eval` + `/eval_tasks` API
+- `/eval` + `/benchmarks` API
 
 This guide goes over the sets of APIs and developer experience flow of using Llama Stack to run evaluations for different use cases. Checkout our Colab notebook on working examples with evaluations [here](https://colab.research.google.com/drive/10CHyykee9j2OigaIcRv47BKG9mrNm0tJ?usp=sharing).
 
@@ -21,7 +21,7 @@ The Evaluation APIs are associated with a set of Resources as shown in the follo
 - **Scoring**: evaluate outputs of the system.
   - Associated with `ScoringFunction` resource. We provide a suite of out-of-the box scoring functions and also the ability for you to add custom evaluators. These scoring functions are the core part of defining an evaluation task to output evaluation metrics.
 - **Eval**: generate outputs (via Inference or Agents) and perform scoring.
-  - Associated with `EvalTask` resource.
+  - Associated with `Benchmark` resource.
 
 
 Use the following decision tree to decide how to use LlamaStack Evaluation flow.

docs/source/concepts/index.md

@@ -42,7 +42,7 @@ Some of these APIs are associated with a set of **Resources**. Here is the mappi
 - **Tool Runtime** is associated with `ToolGroup` resources.
 - **DatasetIO** is associated with `Dataset` resources.
 - **Scoring** is associated with `ScoringFunction` resources.
-- **Eval** is associated with `Model` and `EvalTask` resources.
+- **Eval** is associated with `Model` and `Benchmark` resources.
 
 Furthermore, we allow these resources to be **federated** across multiple providers. For example, you may have some Llama models served by Fireworks while others are served by AWS Bedrock. Regardless, they will all work seamlessly with the same uniform Inference API provided by Llama Stack.